https://github.com/zed-industries/zed/pull/26454 In this PR, we
separated painting for text line into two parts: `paint` and
`paint_background`. This allows selections to appear in front of the
text background but behind the text itself in the editor.

The `paint_background` method was implemented for `ShapedLine` but not
for `WrappedLine`. This PR adds that, fixing the background rendering
for inline code blocks in Markdown, as they use `WrappedLine`.

Before:
<img width="160" alt="image"
src="https://github.com/user-attachments/assets/81466c63-6835-4128-ba22-1b63f5fd7b1f"
/>

After:
<img width="160" alt="image"
src="https://github.com/user-attachments/assets/3b7044d7-265b-45db-904c-3b70fdf421fe"
/>

Release Notes:

- Fixed missing background for inline code blocks in the editor hover
tooltip.